The object of the proposed research is to understand the biochemical mechanism by which neurotransmitters are released when a nerve impulse reaches an axon terminal and to determine how various drugs and polypeptide neurotoxins alter the release process. The studies will be performed on neuromuscular preparations and on subcellular fractions prepared from rat brain and from electric tissue of Torpedo California. Neurotransmitter release and the activities of enzymes postulated to be involved in the release process will be measured as a function of treatment with drugs and neurotoxins. Experiments that have demonstrated the biochemical mechamism of action of beta-bungarotoxin will be repeated with botulinum toxin and tetanus toxin.